1. Field of the Invention
This invention relates to hydrokinetic torque converter for motor vehicles, more particularly, the invention pertains to a torque converter having a bladed turbine wheel, bypass clutch and clutch damper.
2. Description of the Prior Art
Torque converters for automatic transmissions conventionally employ a one-piece turbine hub, on which hub a bladed turbine wheel is rotatably mounting for rotation about the central axis of the torque converter. The turbine hub is joined by a spline connection to the turbine shaft, a transmission input shaft which carries torque from the engine to planetary gear sets that produce multiple speed ratios. Engine torque is transmitted through the turbine hub and the axially directed spline to the input shaft. In normal operation, the torque converter contains hydraulic fluid at fairly high pressure, which causes the impeller cover to distort from its normal shape. Distortion coupled by the engine torque amplified by converter torque ratio causes the spline connection between the turbine hub and turbine shaft to lock, thereby inducing excessive load on the engine crankshaft main thrust bearing. Furthermore, the distortion causes a leakage gap particularly in the region between the impeller exit and the turbine entrance in the converter torodial flow path. This leakage causes converter inefficiency.
Distortion of the impeller cover causes movement of the impeller wheel toward the transmission gear sets and movement of the impeller cover toward the engine. The turbine also moves toward the converter cover when the bypass clutch is operating in the lockup mode due to hydraulic pressure in the torodial flow path. Torque converter ballooning leaves an excessive gap between the impeller and turbine. Engine torque, which is transmitted from the engine crankshaft through converter cover to the torque converter and is amplified by the torque converter, causes locking of the spline connection between the turbine hub and input shaft. Due to the large hydraulic pressure on the converter cover during operation with the bypass clutch open, the torque converter moves toward the engine causing deflection of the engine flywheel and loading the engine crankshaft until deflection of the flywheel exceeds the gap between the turbine and impeller. If the flywheel is rigid, its deflection will be less than the gap between the impeller and turbine, and the crankshaft will be continually loaded due to distortion of the impeller casing.